The passive form of the sentence is “Will those happy days ever be forgotten by me?” Also the correct active sentence would be - “Shall I ever forget(not forgot) those happy days ?
Active sentences in the simple past tense have the following structure: Subject + past tense form of the verb + object Passive sentences in the simple past tense have the following structure: Object of the active sentence + was/were + past participle form of the verb + by + subject of the active sentence