Does anyone know how I could possible play my music of blackberry through a basic 57 plate merc stereo I’m not sure if can plug in a 3.5mm jack from phone to stereo not sure if it has it on the front of stereo or not? My re writers knackered on laptop and can’t face top 40 on radio this evening please any help will be greatly appreciated!
You can’t I don’t think, the newer ones have an aux jack but a bit silly & useless me thinks as there’s no cubby hole to put your phone etc into up where the head unit is. You would need an aux cable more than 2m long, if you let it hang straight down & it might disturb you during your 49.5mph drive-my advice is to get youself some personal earphones or go work for a half decent company that use half decent trucks… 
If you can get the radio out there should be an aux input on the rear. I think it is stereo/twin phonos not 3.5 mm jack, but I’m not certain. Otherwise you could get an FM radio transmitter thing; they’re only a few quid and are better than headphones.
I made a cable for my Axor - it is “plumbed in” and runs inside the trim and dash from the radio down to the phone mount on the dash. I can use it to play music from my phone and the audio from my laptop when watching DVD’s etc. In other trucks I have a 1.8 m cable which can be routed from the sun visor down. Only takes 2 mins to set up.
Poundland do extension leads and the 3.5 to 3.5 lead for you’ve guessed it a pound each I’ve use them they do the job
Hth