That 3M tape comes in 2 widths; you can get by with either. Having just done both front doors this summer, let me offer some advice. Remove the trim strip completely, and clean off ALL the old adhesive on its back side. Paint thinner is OK, but the NAPA store that sells the 3M tape also sells 3M General Purpose Adhesive Cleaner which works better. Be prepared to use elbow grease and patience! Also, clean off the mating surface on the door, so there is absolutely no old adhesive or dirt, and do not wax that area! Wax acts almost as a release agent for the adhesive.

Might be a good time to use your favorite vinyl protectant (Armorall, etc.) on the outside of the trim.

Lay your clean trim strip out flat. if it's curled, use a hair dryer to warm it (a hot garage floor in Phoenix summer heat worked for me...) so it lies flat. Apply two strips of the tape - you'll see where - and go completely from end to end, then trim off any excess with a utility knife. Press along the length of each strip to make sure it's completely stuck to the trim piece.

Before you tear off the film to expose the fresh adhesive, do a dry-run of aligning the trim on the door. The little alignment bumps on the trim broke off when you removed it from the door, but you can see where they went. I pretty much used the bottom of the door and the location of the trim strip on the rear doors as a height guide, and left-to-right was by eye. The point is to get an idea of alignment before you do it for real.

Once you stick it on the door, again press firmly along the entire length, top and bottom, to ensure good contact of the adhesive.

I don't mean to make it sound complex - it isn't. But I tried to do an in-place fix the first time, and the results were lousy.