Can I use this power cord with my charger?
From the comments:

I'm assuming it means it means how much voltage it can transmit to the appliance depending on the power coming in from the power socket. I understand there will be some resistance built into the charging brick itself for safety purposes, but would it be enough to handle the 50V difference in the worst case?

Close. The 300 V is the maximum voltage the insulation between the wires in the cable and the pins and sockets in the connectors can withstand. That means it is rated for use at any voltage up to 300 V. Your supply is probably 230 V so the cable is more than adequately rated. (The cable doesn't generate a higher voltage. It's just copper wire.)

I was researching and as I read online, it said it is important to match the voltage ratings.

You need to match the adaptor to the mains voltage, not the cable maximum voltage rating.

I'm more concerned about the 300 V rating which will be plugged into the charging brick even though the charger specifies an input of 100-240V.

Hopefully it's clear that this is not an issue.