Ok Guys: connected the SSD to a sabrent USB3 UASP SATA III 2.5 " enclosure. the SSD is a Samsung EVO 860 1 TB. Previously formatted the disk and then used Carbon Copy Cloner to make the HDD clone. Afterwards of 4 hours that it took to make the copy. In settings i selected the SSD to be the boot drive, and then restarted the iMac. R/W speeds are in the 400- 430 mb/s. And still we have to try to put the SSD inside the iMac. I post pictures. The boot process did take a little longer than 1.5 minutes. All is working fine. Definitely faster.