Caliper bolt
 

Guys is there a way to replace my caliper bolt and the square thingy (the one who clamps the cable)because i lost it. I can't find anything like it in my place.my caliper is tiagra

That's not a recumbent specific part so it should be relatively ely easy to find what you need.

1. If you can find a bike shop that's still open, try them. The older the shop the more likely they are likely to have what you need. If they like you it might even be a gimme part.
2. Look around for trash bikes. If you find one that has the cable anchor bolt that you need, grab it and throw everything else away.

Ouch, Tiagra isn't Dura Ace or Ultegra, I know, but I wouldn't dog it out that bad ...

If you have a local bike co-op, they will likely have a mess of brake parts from donor bikes.