No, the Delkin Devices POWER CFexpress Type B 128GB is not compatible with the Fujifilm X100VI.
Fujifilm X100VI has an SD-only card slot (no CFexpress support of any type). Its own product page confirms only SD/SDHC/SDXC card compatibility -- CFexpress Type B uses a physically different connector and cannot be inserted into an SD slot.
What works instead
See all compatible memory card for the Delkin Devices POWER CFexpress Type B 128GB →“Storage Media SD Card (-2GB) SDHC Card (-32GB) SDXC Card (-2TB) UHS-I”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)