Can I do a backup to a flash drive from QBO?

There is no easy way to Backup QBO.  There are a few 3rd parties that make snapshots of everything so that you can rebuild things.

So your best bet might be to just do that on your own.  Go Create every Report for the Company totals, full list of Vendors, etc.  (e.g. P&L Detail not P&L Standard, etc.)  Basically go through every section related to Vendors, Customers, Banks, etc. and Export or write down anything you think would be needed. 

And I'd shy away from a Flash Drive being my primary Backup.  Okay if it is another backup, but too much can go wrong with a Flash Drive.   You can easily get a USB Hard Drive and then have the data on your computer, the Ext. HD and then also on a Flash Drive.  And be sure to use a label maker or white tape that really sticks to write the label on.  Don't just use a Post-It (unless you Scotch Tape the post on real good.)

I can share some information about creating a backup to a flash drive, @nobukoito6-gmail. 

You'll have read-only access to your data for one year after you cancel your QuickBooks Online (QBO) subscription. For more information about data availability and export policies after cancelation, refer to this article: What happens to my QuickBooks Online data after I cancel?.

You can export reports and lists into individual Excel files contained in a zip format. This will be saved to your local hard drive. From here, you can save it to your flash drive. 

To export your report or list:

1. Go to the Gear icon ⚙ and choose Export Data. 
2. Add or remove items from the Reports and Lists tabs by toggling the slider. 
3. Click the All dates drop-down to set the time range of the report. 
4. Once you’re done, click the Export to Excel button. 

In case you need other reports, you can check on the following article on how to export your reports to Excel from QuickBooks Online. 

See the following article for detailed guidance on how to export non-posting transactions and attachments: Export reports, lists, and other data from QuickBooks Online.

I'm always here if you need further guidance in creating a backup file. Take care and have a great rest of the day!

@nobukoito6-gmail 

Convert your data to QB Desktop file format prior to canceling your account. You can open the file later on the trial license.