There are 2 a low side and a high side. I don't remember off the top of my head but they are under the hood and if you follow the ac lines you will eventually find them. They both have black caps and one is smaller than the other.
Alex
RepairPal Certified shops can diagnose and repair your 2000 Mercedes-Benz E320. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.