Does transferring advertisements that include pictures of unveiled women, which involves writing and compiling advertising materials, make working at the advertising company unlawful (haram)? And is it obligatory to search for another job?

As long as the work is limited to writing prescriptions and filling out advertisements that are permissible, there is no harm in it. However, it is obligatory to avoid filling out or distributing advertisements that contain pictures of immodestly dressed women. If it is not possible to limit oneself to what is permissible in this work, then it must be abandoned.