Hi,

You can add a related field for this, suppose you have a field named classification_id in your model, and if you need to show the same in the other model form, add a new field to the model and give the relation as this:
donation_type_id = fields.Many2one('refer_model.name')
classification_id = fields.Many2one('donation.types', related="donation_type_id.classification_id", store=True)
In the refer_model.name you must add the field classification_id
classification_id = fields.Many2one('model.name')

for eg when you try to add an employee number in the hr.employee model into another model
hr. employee :

employee_number = fields.Integer('Employee Number', copy=False,readonly=True)

your model :

nominee_id = fields.Many2one('hr.employee')
employee_number = fields.Integer('Employee Number', copy=False,related='nominee_id.employee_number',readonly=True)

you can try this way

Hope it helps