I thought this type of wheel was a cassette type w/multiple cogs not a freewheel. If i can just thread on a cog, what type do i need to get and do i need some sort of spacer for the chain alignment also if i can just thread a cog on do i still need to weld/immobilize the coasting aspect of the hub?

I'm ******** when it comes to anything over a 20" bmx so sorry if i come off as a little dumb.