is it really an unused "partition" or do you mean 127gb of unused "space"? Assuming you actually meant that it's a partition, you should examine the partition's "type" as set in the partition table and format the partition accordingly. For example, if you found out that the 127gb is set to type 83 (linux, ext2) then you could format it via
(assuming that it is the 2nd partition). You should post the output of
and we may be able to offer you more specific advice.