SonOfTheWolfs is correct - Bonus items from The Park can only be redeemed to TSW Classic, not Secret World Legends. The TSW Classic account does not need to be linked to Steam.
If you haven’t yet used the TSW Vanity Transfer service, vanity items (not talismans) from your TSW Classic account can be copied over to a linked Secret World Legends account. You can read more about that service, including its requirements and limitations, here: Legacy Transfer vs Vanity Transfer