I missed taking my folic acid tablet in the first trimester of my pregnancy. my 3rd month scan report is normal. will the missed tablets have any effect on my baby?

Unlikely Any Problem: Vitamins promoted in pregnancy based on limited data & because cheap, concern for possibly poor diet choices/variety & showing care (even if of low to no value). For most people in 1st world countries eating a variety of food & with food abundance, (even though public given lots of bad food advice for decades; e.g. Lookup: dietdoctor, taubes, attia, lustig) vitamin deficiencies are rare.

No harm done: Folic acid reduces the chances of neural tube defects, a common birth defect, but we also get folate (folic acid) from our diet so the vast majority of those who don't take it still do fine. While it is wise to take Folic Acid to minimize risk, billions of healthy babies have been born over countless generations before Folic Acid tablets existed. Your baby was not harmed by your not supplementing.

Probably not: Folate (folic acid) is great to take in the first trimester but isn't essential to normal pregnancy. If you only missed one dose, that's not significant. Folate (folic acid) is necessary for rapidly growing cells and continuing now is a good plan.