All foods have some calories, though celery and cucumber are pretty near zero! Carrots definitely do. Check an online calorie counter and calculate your intake accordingly

dmdennis, re your concerns about snacking. As a 65yr old man I start my fast day around 8.00am with a measured amount of porridge with water, about 150 cals plus fruit bringing it up to about 210 cals. I eat nothing until 7.00pm then have my main meal. I find it easy because the porridge is filling and slow energy release. You can adjust the amount by working out the weight shown on the pack. Do not use the micro wave versions. Doing this means you could conceivably allow yourself around 50 cals worth of veg snacks at lunch if you feel you need it. But as they say, “Dont sweat the small stuff”. You may be pleasantly surprised to find that you can manage through the day without snacking.
Good Luck.