How can I connect pendrives in my USB 3.0 port

USB 3.0 ports are identical to regular USB 2 and 1 ports, so you should be able to just plug your pen drive into the ports.

If you are not able to, then you do not have USB 3.0 ports. You may possible have USB-C ports if your MacBook Pro was made in the last 3 years. In which case you will need an adapter: USB-C to USB Adapter - Apple

MacBook Pro - Technical Specifications - Apple

Are you talking about USB-C? If you have USB 3.0, then you should be able to plug anything into them normally as they are normal USB ports. They are also backwards compatible with regular USB 2 devices as well. In this case you would simply just plug them in. If they aren't USB 3.0 ports and they are USB-C ports, an adapter will be what you need to be able to plug them in. You also can purchase thumb drives that are USB-C ports on them that you can plug in straight.

USB 3 is backwards compatible with USB 2

Using USB devices with your Mac - Apple Support

If the computer has USB 3 ports then just plug it in.

Plug them in.