Hi Friends, I would like to make recordings with my Alisis electronic drum kit connected via usb to the pc but when you have to select it doesn’t give me the alesis strike pro voice. I ask for help please
The USB connection is a MIDI port (not digital audio) and Audacity is NOT a MIDI application. (Audacity has some [u]very limited MIDI capabilities[/u].)
You can record/digitize the analog outputs with Audacity if you have a soundcard or interface with line-level inputs. (The mic input on a laptop will “work” but a line-level signal is about 100 times stronger than a mic signal and you just won’t get good results.)
Or if you get a MIDI application you can change virtual drums/cymbals for different sound after recording and you can move the timing of individual hits, etc.
forgive my ignorance … should i connect a sound card?
No problem. It is easy to get confused here. Your Alesis drum kit supports MIDI and USB. It supports MIDI over USB, but not audio over USB.
Audacity supports also MIDI and USB. It supports audio over USB, but not MIDI over USB. 
On page 10 of the Alesis Strike Pro Performance Drum Module - User Guide v1.5 it says
USB Port: Use a standard USB cable (included) to connect this USB port to an available USB port on
your computer. This connection sends and receives MIDI information to and from the computer.
What this means is that you cannot currently use Audacity to record MIDI commands being sent by your Alesis box over USB. I am hopeful that Audacity will someday support this but I cannot see this happening this month. 
As DVDdoug mentions, you could route the MAIN AUDIO output from your drum kit to a UCA202 or UCA222 (still $19 at Sweetwater), then record the audio via USB into Audacity. You would also need a pair of stereo RCA cables as well as a number of RCA to 1/4 connectors. This should work.
Alternatively, you could explore using a DAW that does support MIDI over USB. Many other DAWs do support this - I would probably start looking at either Cakewalk or Reaper.
I hope this helps. 
Thanks 1000 you were clear