Adapters for Thunderbolt 1 to Thunderbolt 3

Seeing that Thunderbolt 3’s are the new thing can I connect my 2012 imac version 10.13.6 with a thunderbolt 1 port to a new thunderbolt 3 G- Technology G-Speed Drive 16TB with an adapter? Would I still get the same speeds of 40 Gbps with the thunderbolt 3 to my older imac thunderbolt 1 port?