There is a fuel pump relay behind the battery, near the firewall. It is a black rectangular box like relay nested among others. Do a search in this site to get the info.
Did you know that you could it call MB road side 1-800-FORMERC. They will go out, change the fuel pump relay (a common problem)and probably charge you about the same amount of money that you paid for towing. It is one of the benefits of owning a MB, no matter how old. An independent would charge less, or you can do it yourself but, in an emergency...