Wallet #1: empty wallet where all money shall be send to, added this as forwarded address and got a Wallet-ID from bitmixer.io.
Wallet #2: sent from #2 to Wallet-ID, so should be on #1
Wallet #3: sent from #3 to Wallet-ID, so should be on #1
Only want to know if a can send money from 2 different wallets to 1 forwarded address (which a also have access too) bitmixer gave me.
You can send Bitcoins from as many addresses as you like in one transaction but it will link all Bitcoin addresses. Instead, I would suggest you to send Bitcoins from those two to one address and then send Bitcoins from that address to Bitmixer's address.