How to set If in Assembly and then

I'm seraching for an especific value in some EAX need to change it at one especific case.

The code:

If EBX="000080" then

EBX = "0000200"

End If

But I'm running on Auto Assemble. So far if need tho change the value mov ebx,0000200 else mov [esi+48],ebx

How If then can be implemented on Assembly?

mov ebx,200

else

mov [esi+48],ebx