Not perfect, but a good tool to ballpark generic keyspaces.
https://www.grc.com/haystack.htm
as b8vr stated for you it is:
[a-z] = 26
+
[A-Z] = 26
+
[0-9] = 10
+
- _ & = 3
-----------------------
26+26+10+3 = 65
charset = 65
pw length = 10
-----------------------
keyspace = 65^10
65^10 = 1,346,274,334,462,890,625 = 1.346274334×10¹⁸
https://www.grc.com/haystack.htm
as b8vr stated for you it is:
[a-z] = 26
+
[A-Z] = 26
+
[0-9] = 10
+
- _ & = 3
-----------------------
26+26+10+3 = 65
charset = 65
pw length = 10
-----------------------
keyspace = 65^10
65^10 = 1,346,274,334,462,890,625 = 1.346274334×10¹⁸