you need 196 UMS which in real terms is around BBC or a B and two good C's.
Now actual grade boundaires vary depending on what route you take but if you aim for somewhere around 52-55/100 on each paper thats BBB for your A2 and would guarantee your B overall.
You need 420UMS in total. So you have 224 already. You need another 196. 196 is just above a mid-C at A2. Alternatively, if you were to go for an A, you'd need 256 at A2. 256 is 12 marks over an A at A2. Good luck!!
I recognise my post suggests you get slightly over a C, but I am working on the basis (and I tihnk I'm right) that unit 6 is weighted more than units 4 and 5so to be safe I'd aim for BB on units 4/5 and then a C at unit 6 should be fine