I'm bad at dialects, but anyway, let me try to translate your text:
Ahlan. 3am be7ki 3arabe ma3e el numbers 3al internet w kel marra bi shuf el "9" maktub, bas ma ba3rif shu heyde...
Hi. I speak Arabic with the "numbers" on the Internet and I always see the "9" written, but I don't know what it is...
Fi 7ada ba3rif shu heyde el "9", ya3ne shu el IPA transcription taba3 el "9"??
Is there anyone who knows what the 9 stands for, I mean, what the IPA transcription corresponding to the "9" is??
7aredd 3la s2alek (I'm going to answer your question [in a poor mix of dialects I know of]):
M3a el "IPA transcription", fi [sˤ] en nas yekteba "9".
9' > [dˤ]
6 > [tˤ]
6' > [zˤ] wella [ðˤ]
Those are pharyngealized consonants. They mainly have an effect on the following vowel.
For example, "9a" sounds a bit like "saw", while "sa" would sound more like "seh" or "sah".
PS: I don't have any Arab origin, but I've studied MSA ("fos7a") for 3 or 4 years...