If sperm falls and dries does that place become napaak?

Assalamu Alaykum Mufti ,
1) If a couple has intercourse or does something of the sexual manner
and the sperm went onto other things and we cant recall where , what do we do now , especially if the dried sperm doesnt become paak and what if by mistake we walked in some and then it went across the house .. what do we do ?