SMOVE allows you to move a set member from one set to another. You can check if a member exists in a set with SISMEMBER.
➜ docker exec -it redis redis-cli
127.0.0.1:6379> SADD list1 member1 member2 member3
(integer) 3
127.0.0.1:6379> SMEMBERS list1
1) "member1"
2) "member2"
3) "member3"
127.0.0.1:6379> SADD list2 member4 member5
(integer) 2
127.0.0.1:6379> SMEMBERS list2
1) "member4"
2) "member5"
127.0.0.1:6379> SMOVE list1 list2 member1
(integer) 1
127.0.0.1:6379> SMEMBERS list1
1) "member2"
2) "member3"
127.0.0.1:6379> SMEMBERS list2
1) "member4"
2) "member5"
3) "member1"
127.0.0.1:6379> SISMEMBER list1 member1
(integer) 0
127.0.0.1:6379> SISMEMBER list2 member1
(integer) 1
127.0.0.1:6379>