Don't See The EXS24 Sampler, What Do I Do?
If you no longer see the EXS24 Sampler in Logic Pro anymore that is because you are not on the current version of Logic Pro.
The EXS25 sampler is an older synth that was available in all Logic version before Logic Pro 10.6.1.
Double check your Logic Pro version by going to:
Logic Pro > About Logic Pro

If you see that your version is below Logic Pro 10.6.1 then you should consider updating Logic.