Angular custom pipe with number

I have two inputs for the user. The first input is the main number. The second input is the number of zeroes behind the main number.

The basic {{ mainNumber | number: '1.5'}}works. Here I will have five zeroes behind the main number. But I want that 5 to be dynamic, to be what the user has input in the second field.

This is the component.html:

  Number <input type="number" [(ngModel)]="mainNumber" placeholder="Enter the number"> &nbsp;
  Zero: <input type="number" [(ngModel)]="zeroNumber" placeholder="Enter the zero"> <br>
  <hr>
  <b> Number: </b>{{mainNumber}} &nbsp;
  <b> Zero: </b> {{zeroNumber}} <br>
  <!-- {{ mainNumber | number: '1.10'}} -->

  Final number: {{ mainNumber | mojpipe }}

This is the component.ts:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  mainNumber: number = 0;
  zeroNumber: number = 0;
  title = 'shopping-project';
}

This is the custom pipe I tried to build, mypipe.ts:

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({ name: 'mojpipe' })
export class AddZero implements PipeTransform{
    testTwo: number = 1;
    transform(size: number){
        return (size + "."+ this.testDva);
    };
}