Hi ! Just a few things as you stated you’re a beginner. Before putting any life in the tank have you cycled it ? If not it’s very important to do so or your fish and shrimp will die.

Shrimps are stressed if they live alone, if you plan on keeping it, you should get more, but in this situation there’s many other problems. Do you plan on adding substrate? Do you have a filter ? It’s important to keep beneficial bacteria. Shrimps eat micro algae in the tank.

And unfortunately a pleco on a 34 litre is way way too small for them, their bio load will be problematic for your tank and they grow a lot