Please translate/calculate/explain this commission offer?? For a car dealership. ?

You need to talk to the person at the dealership offering you the job.  What is a "retail unit?" Is that mean a vehicle or does a vehicle get assigned more than one unit?  How many units do most first-time salespeople sell?  How many have been sold in the past 3 months?  How do you get assigned a sale?  

Until you have more information, you can't judge whether or not you are likely to make more money or less money.  If you work 34 hours/week @ $13/hour, and work 50 weeks a year, you'll make $22,100 before taxes.  If you get a base of $19,200, you'd need to sell at least 30 units @ $100/each to make more that the retail job.  Is that something you should be able to do in a month, six months, never? 

Base salary is $9.23/ hour if you're working 40 hours a week. It's even less if you're working more hours.  If your base pay + commission equals at least minimum wage for the number of hours you work, the dealership is legally fine.  Personally, I wouldn't take it as the base is too low for working 6 days a week.

Most car dealerships want salespeople that are go-getters, not ones that sit back on their behinds just to rely on hourly pay.  As of a week ago, a friend of mine had sold more than 20 cars at a Honda dealership.  She's been SOTM many, many times because she's a go-getter.

< Which will technically make me more money a year before sales compared to dealership job >

Really?  You can't work this out?

34 hrs/wk at $13/hr = $23,000 a year.

You will definitely make more money with the car dealership IF you sale any cars.

And if you don't, they will cut you loose anyways

= so there is no harm in trying it

You'll mak nost of your income from commissions if you sell.