Right crank/pedal is normally right threaded. Left crank/pedal is normally left threaded.
Most common today are 9/16" x 20 tpi. On old one piece cranks and some other bikes 1/2" x 20 tpi is found. At various times, mostly with vintage bikes pre 1970, you'll find some different thread types and directions.
If you mixed up the crank arms, it makes me think you may have one of those very old bikes that might have different threading's and directions. And maybe won't be compatible with any new pedals.
Put a pic in the gallery here and someone might try to find it. Though you only need 1 more post and maybe a full day to be able to post pics.
Last edited by Iride01; 05-11-22 at 08:56 AM.