Cardio is NOT necessary for fat loss... immediately
Let me preface this with explaining NEAT: Non-exercise active thermogenesis. Basically all the calories you burn each day NOT from exercise. This includes pretty much all movement. The best way to track it with the technology available is using a wearable on your phone to track your steps.
Start out by taking a week to find your baseline of daily steps. Depending on your lifestyle this will vary person to person. Once you've found your baseline, slowly increase it week over week. This will require you to park further away, take breaks at work, walk to the water fountain that's further away and even add in daily walks.
What we're doing here is making lifestyle changes, not just adding cardio for your fat loss goals. These lifestyle changes will carry you much further than just doing cardio every time you workout.
Eventually, you'll get to 15-20k steps a day or more and it will be difficult to get much more. That's the point in time when adding cardio to your routine would be ideal. Again, starting small and increasing over time.
So instead of hopping on the treadmill right away and staying motivated for 3 months before you fall off the bus again just to gain the weight back, make these small lifestyle changes that become habit and have a greater impact in your fat loss goals long term.