How do I get rid of clover mites in my couch??

Wow. Clover mites are normally invasive in late spring/early summer, so the timing of your question is surprising.

Your first step is to stop them from coming in. Any of the yard spray insecticide products can do that if applied in a wide enough band around and up the foundation walls. It may take a second treatment 10 days later, but it shouldn't take more.

For the couch itself, find a product that won't damage the upholstery. Pump sprays and foggers are normally less damaging than aerosols because of the solvents used. The active ingredients for roaches and/or fleas will work on these mites as well as anything. Be certain when treating that you get the interior as well as the cracks between the cushions.

The tricky part will be getting the dead ones off the couch without crushing them. Crushing clover mites will leave a reddish orange stain about 10 times bigger than the bug. Vacuuming very thouroughly followed by using shipping tape as a lint roller GENTLY should remove most if not all of the dead bugs.