Yes that appears to be the overflow kit.
I purchased all of my plumbing stuff assuming it's threaded however it is barbed instead (what you may call nipple)

Return pump is a Sicce 5.00 with a 3/4"
The 3/4" Flex PVC actually seems to be able to get pushed onto the barbed bulkhead end and we probably can glue it on.

It's the 1" drain tube that seems way too tight to fit onto the corresponding barbed fitting