Main Line into House 1" OD Copper, what fitting
In the US, copper &quot;refrigeration&quot; tubing is measured by the O.D. whereas copper pipe sizes are nominal (in other words sized by nomenclature where nothing actually measures to the named size). There is no 7/8&quot; pipe, but there is 1&quot; OD tubing.
It would be very odd to have a copper tubing main line, but odder things have happened. I suspect that, if indeed you are working with tubing, it is a repair that someone cobbled together at that section (rather than the entire main being tubing) because they had some 1&quot; OD tubing on-hand.
It is unclear exactly what your question is, but somebody already converted your tube to FIP (at least on one side) so you should use that; on the other side get a 1&quot; compression fitting to convert to pipe thread as well.