Unless you are using a Yamaha Montage synthesizer to do the recording - this is not the correct forum category to post to.

Here's an official support channel announcement:
https://www.drummerworld.com/forums/index.php?threads/new-site-for-dtx-forums-yamahadtx-com.117274/
... although the link inside seems more marketing than forum. The "DTX Community" is referenced - but I believe this is currently only part of Yamaha DTX's Facebook presence.

Although not necessarily official - here are some alternatives:

http://www.dtxperience.com/forums/

There's some DTX discussion here:
https://www.drumforum.org/forums/electronic-drum-zone.78/

Despite "yamaha" in the URL - this is not an official Yamaha support channel:
https://yamahamusicians.com/forum/viewforum.php?f=145

Since this forum is mostly dedicated to Yamaha synthesizers - you will find users here who have Yamaha non-synth products as part of their gear. So it's possible to find someone else that may help. There are "off topic" forum categories better suited for this type of discussion.

Hello everyone,
I do not know if this is the right place to ask this, so if I was wrong I'm sorry in advance.

I have an old Yamaha electronic drum set, dtxpress 3.
I want to record what I play, to a computer or anything else.

I have no idea at all what I need, from what port I need to do it.

If there is anyone here who can help me what I need to do I will be very happy, thank you very much !!!

Hi bar,
You would do better contacting the Yamaha Drum Department directly. First, as you may have noticed this is a Synthesizer site... and while the relationship is there, the support for the products is actually done by drummers (don’t laugh, that’s going to be important, ultimately).

You’ll want to define a bit more exactly what you want to record “to a computer or anything else”.

In general, you can record MIDI to computer, you can record Audio to a computer. These require different connections and protocols; and may even require additional gear.

MIDI recording documents what you play using a complex series of coded messages that can be directed back to the dtxpress3 and be turned back into sound. You can edit MIDI data, you can notate and print out your drum performance using MIDI data. In order for anyone else to playback the MIDI data they would need to have a dtxpess3. MIDI is not universally distributable to non-players.
Audio recording documents what you play in a more familiar way, the audible sound of the dtxpress3 is documented ... this format can be distributed to friends, family and members of the civilian population (not just gear owner’s)

Many record as MIDI first, correct and augment their performance before rendering it as audio for distribution.

Rather than spend a bunch of time crawling around the Internet, reach out to Yamaha drums, directly. Email, phone, or snail mail...