Migrating Schema to VersionSchema

I'm very new to SwiftData and have run into an issue where I need to change a datatype in a model. I've attempted to implement a migration plan but my original schema was not of type VersionedSchema so I keep getting the following error.

Unresolved error loading container Error Domain=NSCocoaErrorDomain Code=134504 "Cannot use staged migration with an unknown model version." UserInfo={NSLocalizedDescription=Cannot use staged migration with an unknown model version.}.

This is already a released app so I'm trying not to nuke data. Can someone please guide me in the right direction to fix this?

@main
struct AuditApp: App {
    var sharedModelContainer: ModelContainer = {
        let modelConfiguration = ModelConfiguration(schema: Schema(SchemaV2.models).self, isStoredInMemoryOnly: false)

        do {                  
            return try ModelContainer(for: Schema(SchemaV2.models), migrationPlan: AuditMigrationPlan.self, configurations: [modelConfiguration])
        } catch {
            fatalError("Could not create ModelContainer: \(error)")
        }
    }()

    var body: some Scene {
        WindowGroup {
            RootView()
                .preferredColorScheme(.light) // Force light mode
        }
        .modelContainer(sharedModelContainer)
    }
}

import Foundation
import SwiftData

enum SchemaV1: VersionedSchema {
    static var models: [any PersistentModel.Type] {
        [
            WaterSpraySystemAudit.self,
            CannonServiceInspectionReport.self,
            StripAndAssessReport.self,
            
            FileType.self,
            
            AppSettings.self
        ]
    }
    
    static var versionIdentifier: Schema.Version = Schema.Version(1, 0, 0)
}

enum SchemaV1_1: VersionedSchema {
    static var models: [any PersistentModel.Type] {
        [
            WaterSpraySystemAudit.self,
            CannonServiceInspectionReportV1_1.self,
            StripAndAssessReport.self,
            
            FileType.self,
            
            AppSettings.self
        ]
    }
    
    static var versionIdentifier: Schema.Version = Schema.Version(1, 1, 0)
}
    
enum SchemaV2: VersionedSchema {
    static var models: [any PersistentModel.Type] {
        [
            WaterSpraySystemAudit.self,
            CannonServiceInspectionReportV2.self,
            StripAndAssessReport.self,
            
            FileType.self,
            
            AppSettings.self
        ]
    }
    
    static var versionIdentifier: Schema.Version = Schema.Version(2, 0, 0)
}

enum AuditMigrationPlan: SchemaMigrationPlan {
    static var schemas: [any VersionedSchema.Type] {
        [SchemaV1.self, SchemaV1_1.self, SchemaV2.self]
    }

    static var stages: [MigrationStage] {
        [
            migrateV1toV1_1,
            migrateV1_1toV2
        ]
    }

    static let migrateV1toV1_1: MigrationStage = .custom(
        fromVersion: SchemaV1.self,
        toVersion: SchemaV1_1.self,
        willMigrate: nil,
        didMigrate: { context in
            let reports = try context.fetch(FetchDescriptor<CannonServiceInspectionReportV1_1>())
            for report in reports {
                report.ListOfPartsString = report.ListOfParts?.joined(separator: "\n")
            }
            try context.save()
        }
    )

    static let migrateV1_1toV2: MigrationStage = .lightweight(
        fromVersion: SchemaV1_1.self,
        toVersion: SchemaV2.self
    )
}

For reference this was the orignal non versioned setup

@main
struct AuditApp: App {
    var sharedModelContainer: ModelContainer = {
        let schema = Schema([
            WaterSpraySystemAudit.self,
            CannonServiceInspectionReport.self,
            StripAndAssessReport.self,
            
            FileType.self,
            
            AppSettings.self
        ])
        let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false)

        do {
            return try ModelContainer(for: schema, configurations: [modelConfiguration])
        } catch {
            fatalError("Could not create ModelContainer: \(error)")
        }
    }()
    
    var body: some Scene {
        WindowGroup {
            RootView()
                .preferredColorScheme(.light) // Force light mode
        }
        .modelContainer(sharedModelContainer)
    }
}