Lots of threads on this subject...
For the undercabinet fluorescent one, I pulled the fixture, removed the tube & electronics (ballast) and added 4 strips of surface mount LEDs.
Here's the ones I used :
Cool White LED Light Strip, High Density 5050 - 16.4 Feet, 300 LEDs, 5000K, 218 Lumens per Foot. 12V DC https://www.amazon.com/dp/B007C5E3NG..._BOyaBbCV82D2C
I like the cool white versions (5000K)
For your other fixtures, determine your bulb type and search online - Amazon or specialty stores.
You'll be rewarded with better lighting & much longer battery life