Problem connecting Mac to Uno R3

Hello, I'm new here and I try to connect my Arduino R3 to my Mac. (MacOs 10.13.5)
When I try to upload the Blink sketch, I get the message : avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x86
Did I select the wrong board ? (Arduino AVR boards by Arduino > Arduino/Genuino Uno)
If yes, where can I find the right software ?
If no : how can I solve this problem ?
Thanks !!