Macbook Pro 2015 with usb 2 ports need new External hard drive but they all appear to have usb 3 ports. Do I need an adapter? Any recommendations please for Ext H D and adapter.
No adapter is needed for a 2015. Most bus-powered external hard drives these days come with a USB-A to wide micro-B cable, and your MBP still has a USB-A ports. However, you might consider using a hub if you've got an external drive that doesn't have very high current demands. I've got a Seagate Backup Plus Slim 1TB that System Report says only requests 160 mA. It operates fine on an unpowered hub with a USB flash drive and a wireless mouse receiver connected to the same hub.