Adding contacts from iPhone XR to BT' Digital Smart Phone

I suppose this is more for UK members

Recently I upgraded to BT's Advanced Digital Home Phone.  

In reality I very seldom use my BT line as all my numbers are stored on my iPhone XR. However, I would like to transfer these to the new phone but don't know how!  

BT say 'If your contacts are stored on a smartphone or a computer, you need to export these into a .vcf contact file. Once you have the .vcf file, save it to a micro SD card that you insert in the BT home Smartphone. Once you've inserted the micro SD card, follow these steps:

Touch Contacts

Press the Menu button

Touch Import/Export

Touch Import from SD card

Your phone will read the contacts and add them to the contacts list.'

My problem is that I don't know what a vcf file is, never mind how to create one!  Another possible problem is that only have an iPad and an iPhone and I know how Apple like to be different. Can anyone advise me what to do.

Personally I'd have to say that I'm disappointed with this phone adding contacts feels like your back to the early mobiles.