using a power tap outdoors after using it indoors

Try to meet or beat your numbers from indoor.  Don't get overly wrapped up in the details.  The key is simply to measure the work you do and, when appropriate, to push you to do the work or keep you from doing too much.

In general, when I move outdoors I use the same numbers for my zones/targets, etc. unless/until I find that those targets are too easy/hard.  If/when I find that, I adjust appropriately.  You can test outdoors to do this, but you shouldn't need to if you are doing enough riding.

Remeber that while there is definitely science behind training with power, there is still a fair amount of art in training.  Do your best to marry the two.

Use the same numbers and see if they feel the same. I normally get a bump up in my FTP after riding outside for about 6 weeks.

Find a place you can do a TT. See if a local bike shop does one, either go to it or use the same road.

I go out about 40' into a more rural area and my TT place also where I do intervals, I can make all right turns with no stop signs just one yield. I end up making sort of the letter 'p' starting at bottom and ending where curls back to stick. I found it from a LBS's TT I have done.