You can try this one:
=IFERROR(VLOOKUP(A:A,'ARM Requests'!A:F,6,FALSE),IF(AND(A:A="",P:P="Virtual"),"Migrated",""))
However much faster is to use something like this, say in B1
:
=IFERROR(VLOOKUP(A1,'ARM Requests'!A:F,6,FALSE),IF(AND(A1="",P1="Virtual"),"Migrated",""))
and then drag formula down.