If you care about keeping your OS like it is, with all files, programs and settings kept, do the following:
-Create a backup image of your c: drive and eventual other partitions that you have
-boot a setup stick in uefi boot mode. Start windows setup right to the language selection, press shift F10 to bring up a command prompt and there, launch one after the other:
diskpart
list disk
sel disk x
clean
x would be the number of your boot disk (in case you have more then one disk, else, it is always 0)
-close the command prompt and install windows clean
-restore your image of c: over the newly installed c:
Done! You know have converted to UEFI/GPT and may use bitlocker with TPM 2.0.
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That said, what you could also try in case you have windows 10 v1703 or newer, is to use the command
mbr2gpt.exe, which will convert your drive to GPT at runtime, keeping anything. Just have a backup ready, in case something unintended happens.