The define BLYNK_USE_128_VPINS should be placed in the code before you include the Blynk related .h files, e.g.:
#define BLYNK_PRINT Serial
You can add …
… to you code. But it will not have any effect, because it’s not known and therefore not used in the Blynk libraries.
To have more then 31 but less then 128 VPINS you’d need to modify some of the library files:
I’d prefer not to do that because changes are overwrite with each update of the libraries.