It's a Fujitsu W26361 There isn't a lot of info about it on the net, all the links are rotten.
You have a sata port. You have to use an external power supply for that. Or maybe one of the pins next to it can supply the required voltage, you can use a multimeter to figure it out if you are brave. I guess the white one labeled PWR should be supply some volts. To be safe you can split the power of the other sata ssd or buy something like this:
You also have 2 an mPCIe or mSATA port. It's impossible to tell the difference from a photo, because they use the same connector.
https://en.wikipedia.org/wiki/PCI_Express#Mini-SATA_(mSATA)_variant
Without any more knowledge I would guess at least one of them is an mPCIe. Having 2 sata ports and an 2 mSATA next to it would be strange, they could use the mPCIe for a 3G modem or wifi, it would make more sense in a thin client like this.
If it's an mPCIe you can buy a sata expansion there and even connect up to 4 sata drives. Looks like something like this:
You can convert it to normal PCIe or m.2, the possibilities are endless:
If it's not mPCIe but mSATA, you can buy mSATA SSD there, they are really rare nowadays. Or you can buy an mSATA to SATA adapter:
No it's an RDP (Remote desktop) client