The basic rules for changing or converting direct speech into indirect speech with questions:
Remove comma and inverted commas. Use full stop (.) in place of a question mark (?).
Converting direct speech to indirect speech with questions 'that' is not used.
If the reporting verb is in the present tense, change it into the corresponding past tense. If it is in the simple past tense, change it into the past perfect tense.
An interrogative is always either "asked" or "enquired" in reported speech. Hence the subject and verb of the reported speech would be, "He asked".
The pronoun for the listener, in reported speech, will change according to the object of the direct speech, which in this case is "her".
The interrogative sentence is beginning with an Auxiliary Verb - "Can". Thus, the indirect speech will have to be joined by using either "if" or "whether".
The present simple tense (V1st + Subject + Object) of direct speech should be converted into the past simple tense (Subject +V2 + Object) in indirect speech.
From the following rules, we get the correct sentence as "He asked her if she could work on Saturdays."