for sr_line in self.ssr_line:

convert_currency = self.vendor.property_purchase_currency_id.id or self.env.user.company_id.currency_id.id

amount_convert = company_currency.with_context(date=self.date).compute(sr_line.vendor_price, convert_currency)

company currency is current company currency_id and convert currency is currency_id to which you want to convert

i use

currency.with_context(dict(self._context or {}, date=fields.datetime.today())).rate

for my requirement can you pls update your answer i will acpt your answer

Sorry I don't get it . Did you need the exact answer for your requirement.