I bought a small 10 dollar mic from amazon to use when i record videos on my phone but it doesnt seem to work. The part you plug into the phone has 1 line if that is any help.
Sounds like you got a mic with a standard mono plug. I’d say any phone made this decade idnit has a 1/8” jack is designed for a combo headset type plug. That mic won’t work.
To try and clarify, since it seems nobody got what I posted... The JACK is almost certainly expecting a TRRS plug, i.e., for 2 stereo output (earbuds) + 1 input (mic), as is common on the headsets that come with your basic smartphone these days. At least I've got a pile of them from 3 or 4 generations of iPhones.
You could get a splitter and just plug the mic into the mic jack.
P.S. (Edit) But, as [MENTION=178786]rob aylestone[/MENTION] replied in the duplicate post, it's likely the built-in mic is at least as good as a $10 external one. The only reason to use an external would be to allow positioning it much closer to the source, IMO.