is the editor of cosmographie about the writings of the traveler
Masudi regarding the conversion of the Khazars Menhen?i need more
information about the name of thr volume or the author as a reference
in my reasearch.

Hello.

The editor's name that you're probably looking for is "Meynard."

C. Barbier de Meynard was the editor of a French translation of
Masudi's writings. Meynard's translation originally consisted of nine
volumes and is considered an important source on the history of the
Khazars. Meynard's volumes have been in and out of print for well over
100 years.

The work is cited on many web pages, such as:

Hebrewhistory.org:
"Al-Musadi, Muruf al-Dhabad ("Meadows of Gold" [and Golden Stones])
II; Musudi Les Prairies d'Or, text and translation C. Barbier de
Meynard and Pavet de Courteille, 9 vols. Paris, 1861\1877, 2: 9-12,
15, 18-25; 3:61-65."
http://www.hebrewhistory.org/factpapers/khazars23.html

Khazar Studies: Primary Source Documents:
"Al-Masudi, Abu al-Hasan `Ali. Les prairies d'or. Trans.
Charles-Adrien-Casimir Barbier de Meynard and Abel Pavet de
Courteille. Paris: Societe asiatique, 1962. Originally published in
1861-1917. Translation of Muruj udh-Dhahab wa Maadin ul-Jawahir."
http://www.khazaria.com/khazar-biblio/sec7.html

Varchive.org: Beyond the Mountains of Darkness:
"Masudi, Muruj al-Dhabab, ed. Barbier de Meynard and Pavet de
Courteille (Paris, 1861-78), VI, 124ff."
http://www.varchive.org/ce/baalbek/khazars.htm

A 1971 reprint of Meynard's translation is available at the Library of
Congress. See the LOC catalog for more information.
http://catalog.loc.gov/cgi-bin/Pwebrecon.cgi?v3=1&DB=local&CMD=010a+75556227&CNT=10+records+per+page

search strategy: khazars, masudi

I hope this helps. Good luck with your research.