That’s a POL, or Prest-O-Lite, fitting. It’s an older design, lacks some safety features that the new design has. Key features are the male thread and the bullnose tip.
The newer design, usually found on gas grill regulators and smaller tanks, is called a QCC, for Quick Closing Connection. It has female threads, and incorporates safety features such as an OPD, or overfill protection device, and excess flow shut offs.
You are probably used to QCC as are ubiquitous on grills etc these days. As previously mentioned there are converters to allow connecting a QCC regulator to a POL tank.
Btw always remember you MUST keep tanks upright! Propane in a tank is liquid under pressure, with pressurized vapor above it. That’s why the OPD is important. The regulator works only with vapor, getting liquid propane into the regulator or feed lines is a very hazardous situation. If you want an idea of the hazard level you can reach with propane google “bleve”, which stands for boiling liquid expanding vapor explosion. Even. Hundred pounds will make a big blast.