Lately receiving annoying pop-ups from 123greetings that have nothing to do with greeting cards. Appear every time i turn on computer and on every site i engage. Says they are "via Firefox".Thats why im turning to you for help.I am not technically oriented, so stating the solution as simple as possible would be appreciated. (I had a 123greetings account, which I deleted in hopes of getting rid of them. No luck.) Thanks for your help.

PS-Recent scan from Malwarebytes suggested 2 pups??? but they were quarantined. Problem persists.