How can I treat mouse input in Unity for an FPS as a Vector2 like Input.GetAxis or a virtual joystick

Hi StackOverflow community, I have one common issue and need your help. I am a newbie in Unity but trying each day to improve my knowledge, sooo... Recently, I completed one of the Udemy courses and now trying to add new features and run the game on a Mobile device. I added a Virtual joystick asset and already changed movement with that Joystick. But for aim functionality, it is hard for me to change to Joystick.

What I changed already:

//moveInput.x = Input.GetAxisRaw("Horizontal"); // PC
//moveInput.y = Input.GetAxisRaw("Vertical"); // PC

moveInput.x = movingJoystick.Horizontal; // Mobile
moveInput.y = movingJoystick.Vertical; // Mobile

But now I need to change Vector3 mousePos = Input.mousePosition; to something similar to weapon.Joystic.Horizonral as I did with movement.

Please, advise some good implementations.

Here is a part of the code that handles character's and weapon rotation:

if (canMove && !LevelManager.instance.isPaused)
        {
            //moveInput.x = Input.GetAxisRaw("Horizontal"); // PC
            //moveInput.y = Input.GetAxisRaw("Vertical"); // PC

            moveInput.x = movingJoystick.Horizontal; // Mobile
            moveInput.y = movingJoystick.Vertical; // Mobile
            
            moveInput.Normalize();

            //transform.position += new Vector3(moveInput.x * Time.deltaTime * moveSpeed, moveInput.y * Time.deltaTime * moveSpeed, 0f);

            theRB.velocity = moveInput * activeMoveSpeed;

            Vector3 mousePos = Input.mousePosition; 

            Vector3 screenPoint = CameraController.instance.mainCamera.WorldToScreenPoint(transform.localPosition);

            if (mousePos.x < screenPoint.x)
            {
                transform.localScale = new Vector3(-1f, 1f, 1f);
                gunArm.localScale = new Vector3(-1f, -1f, 1f);
            }
            else
            {
                transform.localScale = Vector3.one;
                gunArm.localScale = Vector3.one;
            }

            //rotate gun arm
            Vector2 offset = new Vector2(mousePos.x - screenPoint.x, mousePos.y - screenPoint.y);
            float angle = Mathf.Atan2(offset.y, offset.x) * Mathf.Rad2Deg;
            gunArm.rotation = Quaternion.Euler(0, 0, angle);
        }