You can't easily sync over usb. The only method where you could kinda do this would be to set Firefox to be on the sdcard (if your device has one) and then mount it and copy the desktop profile over. It is a complicated manual process and it would be a one way only, either you copy your thrive data to your computer or the reverse. There is no way to merge the two using usb.

We have a service called Firefox Sync that allows you to copy your bookmarks, history and passwords to your mobile device wirelessly. You can read about it at https://support.mozilla.org/en-US/kb/what-firefox-sync and https://support.mozilla.org/en-US/kb/how-do-i-set-up-firefox-sync

Thrive has a USB port as well as a SD card slot. With portable you can go in & copy the bookmarks file from one flash drive & paste it into another with portable installed on it, as I've had to do a few times. I'm not sure windows explorer will cooperate with Android as far as drilling down to the bookmarks file for this version.

You would need both an sdcard and a usb cable to do a one way profile copy.

I strongly recommend using the Sync service. The data is fully encrypted before upload to the Mozilla servers. Only you know what bookmarks, history and passwords are stored.