Ant

I am trying to load Pixelmon Mod onto Minecraft 1.15.2 forge 31.1.37 I have download the Pixelmon Mod (Pixelmon 1.15.2 JAR) and copied it to the MOD folder, when I try to load Minecraft it always comes back with an error message saying File Pixelmon-1.15.2.jar is for an older version of forge and cannot be loaded. Am I downloading the wrong file, can anyone help I have a very excited 8 year old and I am stuck Thanks Ant