You should be able to use something like Eshopps flex hose to attach to the drain fitting to the sump and 3/4 vinyl hose from your pump to the barb for the return. It is a real basic set up and may be a bit noisy, but that looks how the prior person ran it.
Another option would be to cut the silicone and remove the pipe and bulkhead completly. Then rebuild the drain with new bulkheads and pipes as a herbie. Them run the return up the back and over the tank. That would be a nice quiet set up. Problem is in getting those bulk heads out. Never seen them installed that way. Concern is if you start loosening them but can’t get them out, and can’t tighten them back your stuck.