You can try to get around that, these may work:
=VLOOKUP(VALUE(PASTE!C1),DB!A1:C39,3,FALSE)
or
=VLOOKUP(PASTE!C1,TEXT(DB!A1:C39,"#"),3,FALSE)
But really, if these numbers are, for example, product id numbers which you wouldn't expect to arithmetic on, then they should all (on bothe sheets) be formatted as text, otherwise have them all numeric.