Hi @Emin ,
Thanks for updating.
I assume that button trigger would work for your scenario.
You could consider adding a Button trigger, then specify Date, Minute, Second from the button, using the following function to generate a date and time which will be used in Delay until action later:
concat(triggerBody()['date'],' ',triggerBody()['number'],':',triggerBody()['number_1'])
Add action Convert time zone to convert your local time to UTC.
Add Delay until action, and format the date time with the following code:
formatDateTime(body('Convert_time_zone'),'yyyy-MM-ddTHH:mmZ')
Then once you click the button and give a date time, the flow will be triggered and send an email at the given time.

Best regards,
Mabel