To be sure, I strongly recommend:
* Consulting your owner's manual: It should have a diagram showing the location of service ports for the AC system.
* Searching online for a diagram specific to your year and model: A quick image search for "2001 Chevy Impala 3.4L AC service port" might yield helpful results.
* Checking a reliable online parts store: Sites like AutoZone, Advance Auto Parts, or Napa Auto Parts often have diagrams showing component locations.
Caution: Working with refrigerant requires specialized equipment and knowledge. Improper handling of refrigerant can be dangerous. If you're not comfortable working on your car's AC system, it's best to take it to a qualified mechanic.