How many Centries where Native Americans slaves ... ? Take your time, no rush with your facts.
Many Native American tribes practiced some form of slavery before the European introduction of African slavery into North America.
Native American groups often enslaved war captives whom they primarily used for small-scale labor. Others however, were used in ritual sacrifice, usually involving torture as part of religious rites, and these sometimes involved ritual cannibalism.
The ways in which captives were treated differed widely between Native American groups. Captives could be enslaved for life, killed, or adopted. In some cases, captives were only adopted after a period of slavery.
Some Native Americans would cut off one foot of captives to keep them from running away.
Various tribes also practiced debt slavery or imposed slavery on tribal members who had committed crimes; full tribal status would be restored as the enslaved worked off their obligations to the tribal society. Other slave-owning tribes of North America included Comanche of Texas, the Creek of Georgia; the fishing societies, such as the Yurok, who lived in Northern California; the Pawnee, and the Klamath.
When the Europeans made contact with the Native Americans, they began to participate in the slave trade. Native Americans, in their initial encounters with the Europeans, attempted to use their captives from enemy tribes as a “method of playing one tribe against another” in an unsuccessful game of divide and conquer.
The Haida and Tlingit who lived along southeast Alaska's coast were traditionally known as fierce warriors and slave-traders, raiding as far as California. In their society, slavery was hereditary after slaves were taken as prisoners of war. Among some Pacific Northwest tribes, as many as one-fourth of the population were slaves.
https://en.wikipedia.org/wiki/Slavery_among_Native_Americans_in_the_United_States#Traditions_of_Native_American_slavery
Have another drink.