Generic arrays- how to get data from user

When you read from the console, it always returns a string.
You can't use a Generic specifier to change that to your required type, because that requires a specific Parse (or TryParse, or even Convert.ToXXX) method call to change it.

And there is no specific conversion from a string to any type (unlike in the opposite direction) because there is no way to "know" in advance what the data is, and how it should be converted.
It may be possible to set up a generic "convert from string to my type" method, but only if you add a constraint to the generic class that limits it to classes which implement an Interface which specifically requires such a conversion method to be defined by the class creator.
Unfortunately you can't "back-specify" that for existing built in classes such as the primitive int, double, float etc. so basically you can't do what you want at all.

As already pointed out, there's no standard way to convert a string to a specified class. But what you can do is pass in a delegate to do the conversion, which pushes that responsibility back onto the caller:

class MyGenericArray<T>
{
    private readonly T[] arr;
    
    public MyGenericArray(int size, Func<string, T> parseValue)
    {
        arr = new T[size];
        
        Console.WriteLine("Pls enter {0} no of values", size);
        for (int i = 0; i < size; i++)
        {
            string value = Console.WriteLine();
            arr[i] = parseValue(value);
        }
    }

Usage:

MyGenericArray<int> numbers = new MyGenericArray<int>(42, int.Parse);

MyGenericArray<Person> people = new MyGenericArray<Person>(5, value => new Person(value));

Using Delegates (C# Programming Guide) | Microsoft Docs[^]
Lambda Expressions (C# Programming Guide) | Microsoft Docs[^]