Hello. We have flash drives with USB and external drives with USB only. Is there an adapter that I can buy? What brand do you recommend?
I’m assuming you’re referring to one of the newer MBPs with TB3 (physically USB-C).
For that a simple dongle like this will do.
https://www.amazon.com/gp/product/B099S2HPFW/
In general anything that’s USB will connect to a Mac’s TB3 port and the Mac will treat it as just any USB device connected via USB-C. All you need is to supply the physical connection.
You can use a simple dongle as above or just get the proper cable to replace whatever the device came with. Depending on what kind of USB port is on your USB device, there’s several to choose from such as
https://www.amazon.com/CableCreation-Printer-Compatible-MacBook-Printers/dp/B012V563B6/
https://www.amazon.com/Cable-Matters-Type-C-USB-C-Black/dp/B00UXKTJE0/
https://www.amazon.com/Cable-Matters-Micro-Braided-Jacket/dp/B00UUBRX0Y/
https://www.amazon.com/Cable-Matters-Mini-Feet-Black/dp/B00UUBS0SS/
As long as the physical form factor fits, all of these will work just fine.
On an older MBP with TB2 or TB1, you’d want to connect straight to the Mac’s USB port. If none of those are available, you’d have to resort to an older TB2 hub with USB ports since TB2 does not directly support USB like TB3 does. Those TB2 docks are getting harder to find new, but there’s tons of used equipment around that you can buy.
In addition to simple adapters (good for one device on a port) you can also use USB 3 hubs. Either a generic USB3 hub with a type-A connector and an A-C adapter, or you can get hubs with a lot of type-A ports and a type-C cable.
For instance (no recommendation, just the results of a search to prove that such products exist):
4 ports: Amazon.com
10 ports: Amazon.com