How to migrate string format function with "!@@@" from vb6.0 to vb.net?

This:

VB6.Format(text, "!@@@@@@@@@")

indicates that the specified text should be left-aligned within a nine-character string. Using standard .NET functionality, that would look like this:

String.Format("{0,-9}", text)

or, using the newer string interpolation, like this:

$"{text,-9}"

The second on is a little bit trickier. It's indicating that the specified text should be formatted as a number, zero-padded to five digits. In .NET, only actual numbers can be formatted as numbers. Strings containing digit characters are not numbers. You could convert the String to a number and then format it:

String.Format("{0:00000}", CInt(text))

or:

String.Format("{0:D5}", CInt(text))

If you were going to do that then it's simpler to just call ToString on the number:

CInt(text).ToString("D5")

If you don't want to do the conversion then you can pad the String explicitly instead:

text.PadLeft(5, "0"c)