If you are starting out as a translator, you need work. To get work, you have to apply, most likely to agencies. You could start your own list, entering the details into an Excel spreadsheet. You could also hire someone to collect the details for you on Fiverr or some other similar service. This will cost you a fortune.
In case you weren't aware, there is another solution, which is to purchase someone else's agency list. That way, you don't waste too much time or money on this endeavor. I have included a sample of the list that I compiled, so you have a small list for yourself to use however you want or need to. The master list has over 7,000 entries, and I do charge for it to compensate for the work I have put into it. Contact me if you are interested.