New
#1
Windows will normally create a logical partition for the 4th drive due to a limitation on the number of primary drives.
It looks like you have nothing on the logical drive F, so you should be able to just delete it in Disk Management.
That space will then become "unallocated space" and you could then extend D to take up that space.
If you want to add that space to C rather than D, you will need a third party tool such as Partition Wizard.
Thanks m8 Partition Wizard worked perfectly