The user manual and the quick installation guide (PDF files, sigh) from the Huawei web server are not completely compatible with Ghostscript/Ghostview version 7 and 8 (including the latest and greatest gs/gv versions) and partly unreadable. Huawei does not offer a PostScript file for a PostScript-compatible printers either (kind of "industry standard", sigh). That tells me a bit about the company and I hope you got the modem for free. Anyway, I have to make a few assumptions.
I presume that the modem uses an IP address like 192.168.0.1 or
192.168.1.1 by default. It could be also something like 10.0.0.1. As far as I can see, there is no detail information in the manuals.
I assume you have the two utilities called `arp' and `ping' at hand. IIRC they are part of most MSDOS/Windows, Mac OS and Linux/BSD distributions, and something like that is certainly available for more advanced systems. Try Google if you are not familiar with your operating system and these tools.
First see which ethernet MAC addresses you find with "arp -a" (something like AA:00:04:00:6A:04; 6 bytes, hexadecimal numbers, each separated by a dash or colon), maybe after a reboot of your computer. Then connect the modem to your LAN (local area network) and try to 'ping' the modem from your computer with a broadcast ping, e.g. with "ping -b 192.168.255.255" (or maybe without the option -b). Then try "arp -a" again. If you are lucky, then you should find the new MAC address of the modem. Some devices ignore ICMP-based messages, like the ones sent via ping. You may also have to try different broadcast IP addresses. I hope you will find the MAC address.