Hi @PowerApps11 ,
The question is: will the input texts always be 6 digitals/numbers? I made a demo with inputting 6 numbers and for your reference:

Formula for Default of the Text Input:
Replace(
Replace(
TextInput1.Text,
Len(TextInput1.Text) - 1,
1,
"x" & Left(
Right(
TextInput1.Text,
2
),
1
)
),
Len(TextInput1.Text) - 3,
1,
"x" & Left(
Right(
TextInput1.Text,
4
),
1
)
)
You can and replace the TextInput.Text with Parent.Default on your end.
Hope this helps.
Best regards,