How to build old Ionic 3 project now?

I have an ionic app I built in Dec 2017. I now need to make some simple updates to it. I can’t seem to get it to build and run. I keep getting various package errors, depending on what versions of node/npm/ionic/cordova/dependencies I try. I may get an error about package X, so I fix that and then get another error about package Y, and so on. It’s been several days of fighting with dependencies and still no real progress. I have it in a git repo with a package.json file, but I suspect maybe I had done some npm installs without the --save option so my packages.json did not perfectly reflect my dev box at the time. I’m not very experienced with npm - is there some way to restore exactly what ionic/cordova/npm packages would have been present at the time so I can rebuild this old project?

Any help is appreciated! My ionic/cordova/npm experience is pretty limited so I might be missing something silly.