Cannot install OpenWRT onto MR3010

Hi!
I've tried to update the firmware of my TL-MR3020, but when I upload openwrt-ar71xx-generic-tl-mr3020-v1-squashfs-factory.bin, I receive this error:

Error code: 18005
Upgrade unsuccessfully because the version of the upgraded file was incorrect. Please check the file name.

Here are the steps I took:
- Downloaded "install_piratebox.zip" and "openwrt-ar71xx-generic-tl-mr3020-v1-squashfs-factory.bin"
- Extracted and transferred the "install" folder directly to a FAT32-formatted USB drive
- Safely removed USB drive and connected to router, then plugged the ethernet cable and usb cord into the computer
- Accessed router's Web GUI, and attempted to upload the squashfs-factory.bin file under Firmware Upgrade
- Received error message


Any ideas? Thanks!