Pretty much what prouleau said. How many you do per day depends on how much time you have and how much you can handle in a day. I’ll give a couple examples for reference if you need them.
Example ①
Let’s say you can only do 100 reviews per day and you do your reviews at 8AM and 8PM. Simply do 50 at each time until the pile is gone.
Example ②
You can do 120 reviews in a day but you only have time to do reviews between 7PM-10PM. In this case do 40 reviews every hour so you don’t overwhelm yourself. It’s a lot easier to do reviews in multiple small batches with small breaks in between.
Example ③
You’ve got literally the entire day to do reviews. Just do between 10-20 every hour and you’ll be through it in no time.
You may also want to stop doing lessons until you get rid of the pile. Your pile is small enough that you could probably manage without stopping lessons though. Just keep in mind that the number of reviews you do in a day should be above the amount you get per day and you’ll get through it. People have overcome piles of over 1000 reviews so you can do this.
I’ll also point you to this guide in case you haven’t seen it yet. It’s got lot’s of good advice in it. My Journey of 368 days (+ The Ultimate Guide for WK 
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