Yet another one where the PBP manual explain it all, but no one seems to bother reading Just kidding

ADCIN ADCHannel, Var

ADCHannel must be a decimal value, 0,1,2,3,4,5 etc... you use the ADC channel number, NOT the port PIN name.

ADCIN 0, Var
ADCIN 1, Var2
plah plah plah