Can I blend 3 years of taxes to get the $850 that I owe paid. I paid extra in taxes. Can you blend 3 years?

What exactly do you mean "blend"?  Each year is separate.  Why do you owe $850?  For 2018 or a past due?  They will automatically take out anything you owe from a refund.  

I owe $850 because I did not have insurance

It is still not clear what you mean by wanting to "blend" your taxes.  

You said, the IRS would deduct the money I owe from this return of $950.00. This is what I need please

There's nothing extra to do. IRS has it's eyes on your refunds.

send a check for what you can afford to the IRS payable to US Treasury..

Write "For year 20nn form 1040" and your SSN on the check. Start with the most recent year and any extra will apply to the prior year.

Interest will continue until you have paid it all off.