For 3ds max there are a few DFF exporters;
1) https://gtaforums.com/topic/838479-dff-importer-and-exporter-for-3ds-max (the best.. just not for character skin models)
2) http://www.gtagarage.com/mods/show.php?id=9172 (more outdated and buggy than first one, but does its job). If you plan on using Kams because of its versatility with all sorts of models (including skins), then we advise using this updated 'rework' if at all: https://gtaforums.com/topic/907323-rel-kams-gta-scripts-2018/
3) https://www.gtagarage.com/mods/show.php?id=18572 (importer) and https://www.gtagarage.com/mods/show.php?id=19771 (exporter), may not work on newer 3DS versions - read more about these plugins at https://gtaforums.com/topic/507832-dff-exporter-3ds-max-plugin/
*Mod note: edited for knownledgebase