MKR WIFI 1010 Providing 3.3V to breadboard
In short: VCC = 3.3V

The Arduino MKR WiFi 1010 board documentation is not complete. Well, at least they have the warning that the processor is running at 3.3V and the voltage levels of the pins should never be above 3.3V.

The page of the Arduino MKR ZERO has more information in the "documentation" tab. The VIN pin is the 5V power input, the 5V pin is unregulated 5V output (when the board is powered by USB or the VIN pin) and VCC is the regulated 3.3V output.

The term "VCC" means that it is the voltage at which the processor is running. Since it is a 3.3V Arduino board, it is the 3.3V voltage pin. That 3.3V should be used to power sensors. The "Tech Specs" tab at the MKR ZERO tells that it can supply up to 600 mA. That is the same for the MKR WiFi 1010, because the same AP2112K-3.3 voltage regulator is used.