Hi @Manikanta1231 ,
Could you please share more detail about your need? Do you mean want show the Autonumber in the form when creating a new record?
The Autonumber field is generated when the record has been created, so when form turns to be in New mode, the Autonumber won't show.
The workaround is to create a blank record by patch function, and then use Form to edit that record you just created, then the Autonumber will show.
Set the OnSelect of button:
Set(VarA,Patch('Entity Name',Defaults('Entity Name'),{'The Required Fields':""}).'Unique Identifier field');EditForm(FormName) // create a new record with the required fields and save the GUID to VarA
Set the Items property of Form:
LookUp('Entity Name','Unique Identifier Field'=VarA)
Sample:

Hope this helps.
Sik