Hello,
I work with Sonar and Dimension pro sounds.
BUT I would like to buy new PADS SOUNDS in Dimension Pro for exemple...
Where can I buy theses PADS instruments to use in Sonar ?
Thank you
Nicolas

Not many options. Dim pro never caught on among third party developers. It does read sfz files so there are plenty of those around

Yup, read up on the sfz format and you can roll your own presets from samples!
 
Or you could get AIR Hybrid 3 for $1 and check out the pads in there. It comes with over 1200 factory presets.  Hard to not find something you like in there.  Plus the synth is very tweakable to get your own sound.
http://www.airmusictech.com/product/hybrid-3
https://www.pluginboutique.com/product/4-Synth/1545-Hybrid-3 <$1 deal here until Feb 12th, 2018>
 
It's not a sampler, but it has 100 wavetables built-in, as well as the typical VA (Virtual Analog) oscillators to play with.
 
I really like some of the included pads.  It even has multiple pads categories, for example:
 
Action Pads
Moving Pads
Dance Pads
Soft Pads
Bright Pads

Hello !
Thank you for your reply !
Do you think I can buy this product:

 
and use sounds in my Sonar ?
Thanks a lot
Nicolas

You can use Hybrid 3 as a VST instrument plugin in Sonar.  It is the sound generator.  It does not come with loops or samples that you can use standalone in another product.
 
You just insert it as an instrument, the same way you do with Dimension Pro, for example.

Thank you abacab ! But it is not possible to buy directly a sound online ? A SFZ format for exemple ?
Thanks
Nicolas

SFZ format files can be built by you.  Take any .wav sample file(s) and create a text file and save as .sfz with notepad editor.  Then you can play it with any synth that supports SFZ format, such as Dim Pro, or the free sforzando player by Plogue.
 
There are countless online sources to obtain sample collections for free, or paid.  Try Google for that.
 
Everything you need to know about SFZ can be found here, including a couple tutorial videos, and a link to online resources, including 'the sfz format' an explanation of the format by the original developer.  http://www.sfzformat.com/index.php?title=Main_Page

There is 1GB of free wav samples offered by the sound designer Luftrum.  They consist of field recordings made by him of mostly environmental and ambient sounds.  Perfect for pads!  I love these!  http://www.luftrum.com/free-field-recordings/
 
I also bought his sound bank for the iZotope Iris 2 synth, and it is excellent!

For a selection of pad sounds, I would recommend buying Absynth from Native Instruments.
 
Alternatively, buy Kontakt, also from Native Instruments, and then browse online shops like Sampleism or KontaktHub to find patches you want.
 
(I'm not affiliated with Native Instruments - they just give you access to a ton of pads!)

Absynth is older than dirt, and Kontakt is a money pit.