You don't have to solder them the wires just punch down into connectors.
The bigger questions is where do the wires go and is the wire the proper kind used for ethernet. Ethernet is a point to point media. Phones tend to be daisy chained jack to jack. You need the wires to go between 2 locations and only connect a device on each end. Now if your house has all the phone jacks going back to a central location then at least that part is solved. In most cases if the wires are the standard orange,green,blue,brown pairs...ie 8 total wires...then the cable likely will work. If it is the old style phone wire with just 4 wires that are yellow,red,black,green then you have no chance to make it work.