The importance lies in the transliteration. "Mu'jam" (مُعْجَم) sounds like "Mu-jam" to English ears. When typing in a hurry, "Mu 39-jam" replaces the 'j' with the number '39' due to visual similarity on old mobile keyboards (M-u-3-9-jam). Searches for this term are almost always looking for the Urdu PDF of Yaqut's work.
While a perfect "Mu 39-jam Al-buldan In Urdu Pdf" is a myth (due to the typo in the search term), the actual Mu'jam Al-Buldan is an indispensable resource. For an Urdu speaker, reading Yaqut’s entry on "Makkah" or "Multan" is like traveling back in time. Mu 39-jam Al-buldan In Urdu Pdf