turkçe nasil denir... i  didn’t work...which is the correct spelling?

Çalışmadım.

Çalış + ma + dı + m

I  did not  work

It is çalışmadım. As far as I know, when appending suffix, "d" transforms into "t" when it is appended right after one of unvoiced consonants (I´m not sure if this is proper term for this), that is one of:

p, ç, t, k, f, h, s, ş

So, for example, "I worked" (or "I have worked") would be çalıştım, as the suffix is appended right after "ş". In other cases, this suffix would start with "d".

You can find more information about this here:

http://www.turkishclass.com/turkish_lesson_63 (case B, suffix mutation)

http://www.turkishlanguage.co.uk/conmut.htm (suffix mutation)

thank you both for your help