How do I hook up to the floor strainer....no threaded adapter, only rubber inlet

It simply slip-fits onto the end of a garden hose. Once the pump is going, the suction will keep it attached. That being said, you could slip a hose clamp over it and tighten it down once it's on the end of your hose, just for security.

Thanks for the question, the fitting on the strainer is a slip fit. You will slip your suction hose (standard garden hose) into the fitting on the strainer and you will be ready for use.