Looks to have Ethernet ports so to do this and be plug and play you are looking at Powerline extenders with WiFi. Here's a picture. Now you have to figure out what power sockets look like there.
My mother in law lives in Brazil and has a ZTE ZXHN H108N router (DSL). I'm not there and she's not too computer savvy, so I've been asked to recommend a strategy to extend its wifi signal, which is having trouble with the thick walls of the house.
I'm familiar with various wifi extenders in use in the US, but I don't know this router at all and I can't be there to configure it; we need something as plug and play as humanly possible, and we need compatibility with that particular router. Any suggestions MOST appreciated! Thanks in advance.