In Edit mode, name your bones correctly (with the _R or .R suffixe for the right limbs), select all and go into the Armature panel > Symmetrize:
Select your objects, duplicate with ShiftDEnter and in the Object panel > Mirror > Global X (or CtrlMX):
Now parent each limb to each bone: Select the object, shift select the armature, switch it to Pose mode, select the good bone and Set Parent to > Bone.
Second solution: Symmetrize the armature, join all your objects into one, remove one half, give it a Mirror modifier in order to symmetrize:
Now parent the Object to the armature With Empty Groups. It creates an Armature modifier under the Mirror and it generates a series of vertex groups in your mesh, but for the moment the vertices are not assigned to any vertex group. Select a finger with L, select the vertex group to which it is supposed to be assigned to (here f1_R) and click on the Assign button:
When you have finished with one side, the opposite side will work as well, you can apply the Mirror modifier.