Is this line voltage thermostat sufficient?
Six-foot baseboard heaters are sold in varying voltage and wattages. You can buy a 1250 watt, 1500 or even 2-3000 watt heaters in the six foot lengths. So, I would not assume anything about your old heaters. On a 20-amp circuit, you can have a maximum of  3850  watts. So, you might be within that limit, you might not. There's my caveat. So if you're installing exactly what you had, you could be &quot;safe&quot;.
See this chart https://king-electric.com/pro-tips/sizing-the-heater-circuit/