Redistribute unallocated space

Trying to add 730GB unallocated space to the partition to the right of it in Windows Disk Management utility. Right clicked on the partition that I want to move the unallocated space to, then clicked Extend Volume. Went through the process to the finish when I got a typical user friendly windows message:

"The operation you selected will convert the selected disk(s) to dynamic disk(s). If you convert the disk(s) to dynamic you will not be able to start installed operating systems from any volume on the disk(s) (except the current boot volume). Are you sure you want to continue?"

I don't know what that means. I am guessing that I would be ok because the hard drive on which I want to reallocate space is an external HD and does not have an operating system on it but that message scared me so I cancelled. Also I dont know if adding unallocated space to a partition with data on it will destroy that data.

So, I installed an old Paragon program I had - Partition Manager 9. everything went well until the point of using it when a message said there had been a catastrophic failure and my WIN10 could not use it. However, it is on my system in the programs folder and also showing in Programs and Features on Control Panel. But I can't uninstall it. So I went to Paragon, found that there was a free PM14, installed it ok and then found that the Redistribute Free Space button is greyed out.

Is it because it is free so only bits of the program work? I would appreciate a bit of help please. I just want to move that 730GB of unallocated space into a partition and move on.