You can get a rough idea by looking at the asking prices for similar businesses on business for sale web sites. You can also ask intermediaries what they think your business will sell for - most intermediaries are happy to give you an informal estimate. Lastly, Business Brokerage Press publishes a helpful guide with rules of thumb for valuing many different types of businesses. Here is a link to their web page: https://businessbrokeragepress.com/business-reference-guide/.
We do not recommend hiring an appraiser to do a formal valuation. In our experience, appraisals tend to be low, i.e. businesses almost always sell for more than their appraised values.