You are trying to import one application into another which will never work.
Step 1: Export images from Photos in a folder on desktop
Step 2: Open Lightroom and then import that folder into Lightroom.
Thanks I tried that and it worked for 1,000 photos.
Once I import all my photos like that can I safely delete Photos Library?
Yes indeed you can, only after you import all images.
Make sure that you do not delete the folder that you created on desktop.
Thanks Rohit great support!!!!