I have a glk 350, trying to figure out how to get my music from iphone7

I purchased the adapter but i keep getting an error message

 

It could be a few things , I purchased a cable off eBay , it was junk, even missing connectors. Your dealer would be best for a cable. I also found after a phone update MB was months behind, I just use an old Iphone as a music player and leave it in the center consul.

 

not as easy as you would expect (or should be). you have two options really. the MMI from Mercedes, which honestly kind of sucks because it has limited data over bluetooth. these can be found on ebay occasionally for between $100-$200. Or you could buy this thing off amazon and it should get you going without trouble. it took me a while to find the right no fuss solution for our 2012. the phone will still connect to the truck via bluetooth for phone calls, but music streaming will be handled by the tune2air device. it works very well, and nothing to fiddle with. all song, playlist data is populated to the entertainment system and all the factory controls work normally.

Tune2Air Bovee WMA3000A+ Wireless Bluetooth Music Interface Adaptor for in car iPod Integration (AMI/MDI connector)
Link: http://a.co/8XeTSBo

 

I have a 2013 , it has a phone USB jack in the center consul, do you have that ?

 

ah, i assumed OP had Multi Media Interface plug in glove box or center console. I do not have usb but have MMI plug.