If otherwise you don’t plan to use windows on that machine anymore (on bare metal, a virtual machine is not relevant here), it would be better to transfer your data to a Linux native file system. Unless you have a solid preference, ext4 is a good choice.
Basically you just need to copy your files over, but you may need to do it in chunks (and resize the 2 partitions in every round) if you can’t hold the files if the NTFS file system safely while you reformat it.
Also, if you want to keep attributes like file creation time and last modification time, that’ll require a bit more copy parameters, if you want this let me know and I’ll fill you in on the details.
What distro do you use by the way?
bec