You actually don't need to know it very accurately, you can eat at maintenance then add the "cardio activity".

For example, let's say my TDEE is 3000kcal which implies if i eat at TDEE i do not gain or lose weight.

Now, i add some cardio, let's say an hour of fast walking each day.

After 7 days i lost 1lb weight, which means i burned 3500kcal in 7 days since 1lb fat = 3500

3500/7 = 500kcal per day calorie burn from my cardio.

So i can approximate an hour of fast walking for me equals = 500kcal burn.

it works if you know your ACTUAL TDEE not an Estimated TDEE from a calculator, for Actual TDEE see this

1kg (2.2 lbs) fat = 7,700 kcal, so you can do same calculation for kg.

Now, let's do same for tracking calories burned in a lifting session

Human body is not perfect machine, there are loses in system and those loses vary widely per body composition/metabolism etc...

Simple way to calculate is to calculate your maintenance calories let's say it's X calories

Now let's say i engage in lifting session 2x per week.

after 3 weeks, i have lost weight 1lb fat.

Tracking for 3 weeks should take out water weight fluctuations.

1lb fat = 3500kcal so, for per session of lifting i lost fat equivalent of 3500/3x2 = 583kcal

So, each session burned 583kcal

But remember an average 30-minute lifting session only burns about 150-210 calories (Hunter GR et al., J Strength Cond Res, 2003

Don't trust the calorie burn estimate on your watch. A 2020 systematic review and meta analysis by Fuller et al. found that no brand of wearable was accurate within a 3% margin of error more than 13% of the time. The study revealed that these devices are wildly inaccurate. Garmin and Withings wearables underestimated calorie burn in 69% and 74% of tests, while Apple and Polar devices overestimated it in 58% and 69% of cases. These results show that it's common for leading consumer wearables, not just the Apple Watch, to have calorie tracking errors ranging from 15% to over 50%.

The best way to figure out how many calories you're actually burning is to track your food intake against your weight changes over time.