It will appear on your Steam inventory. If you have not received it yet, just wait a bit more. Steam is dropping them progressively to user that owns one of the two games. If you still don't receive, keep waiting more.
this is complicated...i mean if it wont appear in my library in about 2 or 3 weeks then i will buy it myself i have 43,95€ on my steam account anyways
Yeah so the people that have beamng drive or automation can get the code but people that don't have either wont get one because they did not invest in getting one or another. So if you have steam you will get the code. It wont take 2-3 weeks and if it does then there is something wrong on your end. have fun!
A little off topic but i bought Automation Supercharged Edition back in 2014 before it was on Steam and I still haven't gotten my V16 engines.
Please note that the coupon was available only for a limited period (July to August 2018, the maximum period Steam allowed). You should have received it, and by now it would be expired anyway. I'm not sure if V16 are in Automation yet, that's probably material for the Automation forum