I'm going to start with a couple of assumptions, so let me know if I'm wrong on anything because that could drastically change what my answers would be.
First of all, I'm going with the belief that you meant "Elantra" rather than "Electra" in your question. Secondly, my answer is based on the idea that you're talking about an automatic transmission rather than a manual.
Okay, with that out of the way, there are a lot of reasons why an automatic transmission won't go anywhere. The simplest, and possibly the only one most of us home mechanics can take care of ourselves, is if it's low on fluid. It appears your car uses what's called a "Sealed Fluid System", meaning there's no dipstick to check the fluid. So topping up the fluid gets a lot more complicated than just getting out a funnel and filling it till the dipstick reads full. Here's a page from a the Hyundai forums describing the procedure for your car.
Automatic Transmission Level in 2015 Hyundai Elantra
Being a sealed system, there should not be any loss of fluid, so if this is the case, there's a leak somewhere that will need to be fixed, and depending on how badly it's leaking you may or may not need to fix that leak right away. Look under the car where it's been parked for any red (or possibly brown if it's old), oily fluid on the ground.
Other than that, there are many other things that can go wrong with an automatic transmission, but unfortunately very few of them can be fixed by us home mechanics. Here's a web page off a car site discussing possible reasons for transmission failures in your car.
Most Common 2015 Hyundai Elantra gt Transmission Problems - MyCarSpecs United States / USA
Virtually all of those problems listed would need to be fixed by an experienced transmission mechanic, which won't be cheap. I'd suggest that your next step should probably be to take the car to a transmission shop (obviously you'll have to have it towed) and have a diagnosis done on it. You'll almost certainly have to pay for it, but at least at that point you'll know what you're dealing with.
If it was my car and the cost to repair the transmission was prohibitive, my inclination would be to buy a used transmission from a wrecking yard and replace it myself. I'm fortunate in having the experience and tools to do that job but I understand that it is a major repair and not something most people can tackle. Probably the cheapest solution would be to find a mechanic willing to replace the transmission with a used one, but even that is going to run up a significant bill.
These are just my own personal thoughts on this and I'm certainly no expert on Hyundai transmissions. Hopefully some of our other members will have ideas of their own that could help.
Best of luck with your car; let us know how it goes.
Thank you so much for answering.. yes that means so much sense and clear.. yes I'll let you guys know the results