Load Balancing Router

I was choosing a loud balancing router but I failed and I need you to help me please.
Here is my situation. I have 4 internet modems and I want to combine their bandwidth. All of them have only 1 Ethernet port and no electricity in socket or such. So I assume they use that only Ethernet cable for power supply too.
Modems are LTE Cat6 and they can provide up to 300Mbps speed.
I only need 1 LAN output of all the bandwidth combined together on the loud balancing router so I can connect it to a wireless router (which I have to buy too).

Thank you.

with 4-way request, then I think you should choose peplink 580 line, it allows 7 way wan connection