There are two ways that you can accomplish this:
- Using a compatible mSATA-to-M.2 adapter. To be compatible, it must support M.2 Type M or B+M keying and it must fit within the space available in the BN NUC for M.2 adapters. I only found two examples of an adapter that would appear to meet the first (M.2 keying) requirement: Amazon.com: SMAKN mSATA SSD to B key M.2 Adapter and Amazon.com: mSATA SSD to M.2 B Key Adapter. By my eye, however, neither of these adapters will fit in a BN NUC; it looks like the auxiliary SATA Data and Power cable headers on the board are simply too close to the M.2 socket and will interfere with the footprint of these adapters.
- If you purchase the 'H' Model (NUC7i3BNH) instead of the 'K' model (NUC7i3BNK), it provides a bay for a 2.5" SATA III SSD/HDD/SSHD. You could purchase a mSATA-to-SATA adapter that will fit into this 2.5" bay. Here is an example of such an adapter: Amazon.com: Syba mSATA SSD to 2.5-Inch SATA Adapter. I have purchased and used one of these adapters myself and it works great.
From a performance perspective, these two options, because they both rely on a SATA III interface, would have roughly equal performance. As Jason has said, you obviously cannot come close to the performance of an NVMe SSD going this route.
I would be remiss if I didn't also point out that you do have other choices (albeit more expensive if you already have the mSATA SSD). These include using a M.2 NVMe SSD, a M.2 SATA SSD or a 2.5" SATA SSD.
Hope this answers the query,