You'll need a Thunder Stone to make it evolve.
You can evolve Eelektrik by using a thunderstone.
Evolve it using an Thunder Stone.
It evolves with a thunderstone not levels
Elektross does not evolve from any Pokémon; rather, it is the evolved form of Eelektrik, which evolves from Tynamo. Eelektrik evolves into Elektross when it reaches level 39. Tynamo evolves into Eelektrik at level 26, completing the evolutionary line.
Tynamo evolves into Eelektrik starting at level 39. Eelektrik evolves into Eelektross by using a Thunderstone.
Eelektrik, Pikachu and Eevee are the Pokémon that can evolve once you use a Thunder Stone on them.
The only new one to use thunder stone is Eelektrik to Eelektross. Then you have your Pikachu/Raichu and Eevee/Jolteon.
level 50
Eelektrik - Eelektross
You can't find Eelektrik. You have to evolve a tynamo, which can be found in Chargestone Cave (it only has a 2-8% appearance rate)
Tynamo evolves at level 39 into Eelektrik.
Tynamo evolves into Eelektrik at Level 39.