(full title: Dead or Alive Xtreme 3: Fortune for PS4 and Scarlet for PS4/Nintendo Switch) was never officially released for PC. There is no legitimate, legal "PC download free" version from Koei Tecmo or Team Ninja.
However, there is a separate PC-exclusive spin-off that is officially free-to-play. Official PC Alternative: Dead or Alive Xtreme Venus Vacation dead or alive xtreme 3 pc download free
To do this legally, you must own the original game disc or digital file and "dump" it yourself. (full title: Dead or Alive Xtreme 3: Fortune