what is best place to check keyword searches to see which ones are biggest keyword searches?

These are ideas I have. I know just pick one and go – just want to see which one has greatest potential
Are these specific enough? or do I need to drill down more

Nitche ideas
Women over 40 who need to lose 40+ pounds
Women thinking of bariatric surgery
Women who have undergone surgery and gained the weight back. Looks like there 200k surgeries in the US yr
Women who are still holding 30 # plus of baby weight gain

Not sure either would be willing spend money on a $2k 6 wk program

Please share any feedback – thank you tons