Is the pharmacist's request for masks and disinfectants from drug representatives, in exchange for his dealings with them regarding hospital orders, considered a bribe? If so, what should he do for Allah to forgive him?

If the masks and disinfectants were requested with the knowledge of the hospital administration, then there is no blame upon you. Otherwise, inform the administration about it. Gifts from rulers are considered ill-gotten gain unless the Imam permits it, just as the Prophet permitted Mu'adh to accept a gift when he sent him to Yemen. And whatever is gifted to workers because of their authority belongs to the public treasury unless the Imam grants permission.