Change a basic disk to dynamic disk?

Dynamic disks are a pain. Do not deal with them. If you would post a snip of your Disk Management, we could have a look what needs to be done. Apparently you already have 4 primary partitions.

Nice snip - unfortunately I cannot read it. But if you have 4 primary partitions already, then you cannot create another partition unless you want to run into this awful dynamic partition mess. It would convert ALL your partitions into dynamic, and this will be unworkable.

I assume you wanted to use the 58GBs which are apparently unallocated (I think I figured that out without being able to read). If you want to backup your partition, I suggest you use an external disk and image the partition with free Macrium. Watch this tutorial and you will find all the instructions you need. Copying your system to the same drive would not help if the disk breaks.

The 58GBs I would add to D. An alternative would be to delete e.g. this 10GB partition to get to 3 primary partitions. I assume this is the recovery partition. You can burn the DVDs from that and when you have images of your system, you do not need that any more. Then, when you want to create a new partition, you MUST create an extended partition under which you can create many basic (simple) partitions.

I guess you have to postpone your project until you get a bigger external disk.