How so I switch Verizon cell phones?

I was recently given a Verizon cell phone (Model Number CDM8975PTT) by my mother's friend who isn't using it but still has to pay for it because the contract hasn't run up yet. I have another Verizon cell phone (Model Number LG-VX9200) that I would like to activate in place of this one but don't know how. I looked up how to do it and I was told to dial *228 and then enter the ESN code but the back of the phone I want to switch it to only has a MEID HEX followed by 14 digits. I tried an online converter but when I entered in the number it gave me, *228 said my number was wrong. Am I doing something wrong?