It’s never wise to make blanket generalizations, especially when it comes to salvation. We are not elect detectors nor does God call us to be. Many Seventh-Day Adventist’s are true Christians, but this is in spite of official Seventh-Day Adventist teaching, not because of it.
There are many souls caught up in Seventh-Day Adventism that do not believe the damnable heresies the organization teaches. Nevertheless, it is important to know that the organization teaches a false Gospel (Galatians 1:6-9) and proselytizes a false god (2 Corinthians 11:1-4), neither of which can save anyone because they aren’t real. This puts the organization outside the bounds of christian orthodoxy. Because of this, born again Christians should not be associated with a false church.
Christian’s should always be ready to share the true Gospel and Christ with Seventh-Day Adventist’s like we should with all tribes, tongues, peoples, and nations.