Got Minecraft for Windows 10 Free from Mojang - Still asks me to purchase it in game

you have to link your mojan account with the microsoft account so you can claim the code to be able to play the windows version

Players who have purchased Minecraft: Java Edition before October 19th, 2018 can get Minecraft for Windows 10 for free by visiting their Mojang account. Once you've migrated your account, you will be able to claim a code for Minecraft for Windows 10

Did you redeem the code?

Hi MK,

Thanks for asking this question on the Xbox forums. In regard to any codes for a free version of Minecraft for Windows 10 with the purchase of Minecraft Java version, that would need to come directly from Mojang. According to their website, "Players
who have purchased Minecraft: Java Edition before October 19th, 2018 can get Minecraft for Windows 10 for free by visiting their Mojang account."

Should you like to check your ability to claim this code, I recommend following the instructions provided in the Mojang Support article entitled
Minecraft for Windows 10.
If it is determined that you're not eligible, then you would need to purchase that particular version in order to use it.

Give this a try and let us know the results.

I hope that this helps you out!

there are 2 versions, minecraft windows 10 version and mojang minecraft java edition, these are 2 completely seperate games if you purchase the mojang one you still need to purchase the windows 10 version if you want that one.