How do i geotag my drone video post merging 4 video files with different flight path? What are the best software ( free and paid versions available)?

Hi!
You might be better off posting your question in the 'products' section of this forum.
That is way more active.
Just create a new thread here : https://forum.dji.com/forum-129-1.html and select the right category / subcategory. (not sure what the best category is for your question)

Depends on the drone,   some will create an srt file that contains that information,  on the newer models the location is held in the sub titles.