The Latitude D830 had the WWAN card slot with a USB Controller to handle 3G cards and at best the Intel Flash Memory for Vista. Hence the concept of ready boost or whatever it was called in Vista where we can plug a USB drive and get things done faster, at least supposedly
The same was used for this slot as well through Intel flash cache module.
This is not the same as mSATA. mSATA uses a completely different controller and is not USB and can only be found on newer laptops and desktop boards.
I am sorry but you cannot just plug in a mSATA drive into a WWAN slot and expect it to work.
For example, some laptops have a SIM Card slot, but no WWAN card. Even if we enter a SIM, the laptop does not have the necessary hardware to control 3G Wireless.
However, if you just want to add some fast storage to your laptop, you can add SDHC cards using mPCIe adapters for MicroSD cards, something similar to the below link:
MR15 (Dual Micro SDXC/SDHC/SD Cards to mPCIe Adapter)
Hope this helps.