Welcome to Bike Forums.
You'll need a 15mm pedal wrench (very thin so it fits between the crankarm and the pedal). The right pedal is right-hand threaded. The left pedal is left-hand threaded.
If you can't get the pedals loose, take the bike to a bike shop. It'll take then 30 seconds to get them off.
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The Lord is merciful and gracious, slow to anger and abounding in steadfast love. - Psalm 103:8
I am a cyclist. I am not the fastest or the fittest. But I will get to where I'm going with a smile on my face.