I would never ever save a Tiff as a JPEG unless it was going to be used on the web.
Why go from a lossless format to a lossy one?
Anyway – there’s no need to do anything with your images, simply use file>place and place them as they are.
Under Window>Info you can select your image and it shows two readings – Actual and Effective PPI (take that PPI and DPI are interchangeable in this instance).
Actual shows what the image is at it’s actual size.
Effective shows how the scaling of the image has affected it’s PPI in InDesign.
For instance a 72 PPI image placed at 24% would be 300 PPI (72/24*100=300)
If your image PPI is over 300 ppi then don’t worry about say something ridiculous like 947 PPI.
When you File>Export and choose PDF Print go to compression and you have options for
Downsample to and choose your desired DPI output
For images over and choose your desired res to target
For example
Downsample to 300
For images over 350
This means that any image that is over 350 ppi (say 947 PPI as noted above) is downsampled to 300 PPI for print. Which is more than enough for most lithographic printing, and definitely more than enough for digital printing.
Any images below 350ppi in the layout are unaffected, that is any image listed under 350 in effective PPI in the Window>Info panel.
Of course there is lot more to making a print ready PDF – if you have any queries please let me know.