These are millipedes. They can be a nuisance when they get inside, but are harmless as they do not damage furniture, walls, or other materials, and do not bite. Millipedes eat decaying vegetation, so may visit a compost pile (especially with food scraps like vegetable peels), areas with plants suffering root rot or leaf loss (on the ground...they usually don't climb up onto plants), fallen logs in more advanced decay, and similar sites with dead or dying plant parts. They can crawl around on house walls or pavement, but are just wandering around or escaping soil that has become too waterlogged.

As with any insect (or in this case, arthropod) that finds its way inside as a nuisance pest, the key is exclusion. Sealing gaps and cracks with caulk or expanding foam, checking vent covers and pipe entry points on exterior walls for sealant needs, and fixing any torn window screening or worn-out door weather-stripping can all help to deny them access to the inside. If anything that retains moisture is piled against the foundation or near a doorway, like a thick layer of leaf litter, a compost pile, a firewood stack, or if there is a roof downspout outlet that empties close to the building, that can all create conditions appealing to darkness- and moisture-seeking organisms like millipedes. A garage door might be harder to seal, since the seals on the sides or base might not be snug or dense enough to exclude something this small and slender, but it might be worth inspecting to see if there are obvious gaps from cracked or missing material.

We do not recommend (re-)treating the pavement with any chemical insecticide or repellent, and a pesticide is not needed indoors either (nor would one be very effective). Aside from potentially not working, as seems to be the case here, an exterior application might harm beneficial insects or pollinators that come into contact with the spray residues.

Miri

I have had a similar experience seeing hundreds of millipedes wandering over the front stoop and siding of an apartment building, a few years ago during a very rainy spring. They have since essentially disappeared. Unfortunately there are no practical or effective options other than to try to block as much access to the indoors as possible. You could of course consult with a pest control professional if you wish, but other than a perimeter spray that is going to use an indiscriminate broad-spectrum pesticide (which might not be completely effective anyway; millipedes are not insects and aren't affected by the same array of chemicals), we can't think of a method to use any sort of treatment indoors that would be of much use.

Miri